Photographic printing



Patented Feb. 4, 1941 PATENT OFFICE 2 9 0 A. PHOTOGRAPH! PRINTING Edith Weyde, Cologne-Nicki, Germany, assignor, by mesne assignments, to General Aniline a Film Corporation, New York, N. Y., a corp ration of Delaware No Drawing. Original application February 10,

1938, Serial No.

189,762, now Patent No. 2,205,756, dated June 25, 1940.

Divided and 'this application December 16, 1938, Serial No.

246,067. In Germany February 15, 1937 8 Claims.

The present invention relates to an improvement in the p'roduction'of photographic prints. This application is a division of my copending application Ser. No. 189,762 filed February 10, 1938, which matured into Patent No. 2,205,756, June Photographic papers have a tendency to ad- .sorb and thus to retainsodium thiosulfate from thefixing baths and the soluble silver salts produced by the fixing operation. This phenome-- non on the one hand affects the permanence of the photographic print since the retained salts gradually react with the silver. image to; form silver sulfide and the silver salts also gradually decompose into silver sulfide and thus impart a yellow tint to the paper; on the other hand the phenomenon leads to a more or less pronounced coloring of the whites in the toning of the print,

particularly with a sulfide or a selenide, in consequence of the intensely colored silver salts which are formed.

The present invention is based on the observation that the barium sulfate used for whitening the paper s primarily responsible for the undesirable retention of the compounds or salts.

Precipitated barium sulfate has as is known the tendency to adsorb metallic salts (for instance BaClz, MgClz or FeClz) and other com- ,pounds particularly substances having a high molecular weight such as dextrin which itself has a strong adsorbing tendency (see, for instance, Marc, 'Zeitschrift fiir physikalische Chemie, '75, 710, 1911 and 81, 641, 1913). Moreover, it is known that the adsorbing a substance may be afiected by adding a further component. The adsorbing Kongored by means of cellulose, for example, is intensely reduced by adding phosphate ions; It has also been proposed to remove mangano ions which are adsorbed by precipitated manganese dioxide with the aid of solutions of ferrous salts because manganese dioxide is capable of adsorbing ferro ions more intensely than mangano ions (Geloso', Ann. Chim. 6, 352, 1926).

it is one object of my "invention to provide a process of removing sodium and silver thiosulfate being adsorbed by barium sulfate. Another object is the provision of a process of removing the thiosulfates by treating barium sulfatewith' substances having a strongtendency to become retained by adsorption.

Further objects will be apparent from the disclosure following hereinafter. I

Particularly suitable for the purpose of the present invention are the salts of the rare earths.

i It is noted that it is knownthat the hydroxides of the rare earths, the salt solutions of which as well known easily hydrolyze, are capable of adsorbing many substances.

It is immaterial at what stage in the manufacture and preparation of the paper these salts are allowed to act upon the barium sulfate.- They maybe added directly to the barium sulfate grounding or to the emulsion, from which they gradually migrate to the barium sulfate. The desired effect may also be obtained by using such salts in an intermediate bath following the development or as an addition to the fixing bath or even in a separate bath after fixing but before washing. The washing of the paper raw material which may contain the barium sulfate as filling agent may be improved by the substances so that it is advantageous to add them in the preparation of the paper.- However, it is.

also practicable to soak the finished paper material with a solution of the substance.

It will be understood that inaddition to the substances hereinbefore named there is a number of further substances which havethe desired action. However, the use of these substances is in part restricted since it is necessary that there should be no coloration of the paper material or of the bagytes and that the substance should not have an unfavorable effect on the photographic emulsion.

' The following examples illustrate tion':

(1) To 1 liter of a gelatin solution containing barium sulfate such as is used for coating the photographic paper, there are added 3 grams of lanthanum chloride.

(2) To a photographic emulsion there are added per liter 2 grams of cerous sulfate and the emulsion is applied to the paper in the usual manner.

, (3) The photographic material is treated after development in a. bath of the following composition:

Water cc 1000 Glacial acetic acid cc l0 Thorium nitrate; "grams" 10 In this bath the photographic material remains for 1-10 minutes and isfinally fixed.

I claim:

l. A photographic fixing material for photo- :graphic elements having a barite layer and a light-sensitive silver halide emulsion layer thereon, which comprises silver halide fixing agents and an amount of rare earth metal salt the invencapacity of the barite layer for thiosulfates.

2. In the process of producing photographic prints by exposing, developing, fixing with sodium thiosulfate and washing photographic paper having a barite layer and a light-sensitive silver halide emulsion layer thereon, the improvement which comprises immersing said photographic paper after the development thereof in a bath containing an amount of a rare earth-metal salt effective to suppress the adsorptive capacity oi said barite layer for thiosuli'ates.

3. In the process of producing photographic prints by exposing, developing, fixing with sodium thiosulfate and washing photographic paper having a barite layer and a light-sensitive silver halide emulsion layer thereon, the improvement which comprmes immersing said photographic paper after the development thereof in a fixing bath containing an amount of a rare earth metal salt eilective to suppress the adsorptive capacity of said baritelayer for thiosuli'ates.

4. In the process of producing photographic prints by exposing, developing, fixing with sodium thi'osuliate' and washing photographic paper having a barite layer and a light-sensitive silver halide emulsion layer thereon, the improvement which comprises immersing said photographic paper aiter the development thereof in a bath containing an amount of lanthanum 2 v 2,230,710 sufllcient to eflectively suppress the absorptive chloride effective to suppress the adsorptive capacity of said barite layer for thiosulfates.

5. In the process of producing photographic prints by exposing, developing, fixing with sodiumthiosuliate and washing photographic paper having a barite layer and a light-sensitive silver halide emulsion layer thereon, the improvement which comprises immersing said photographic paper after the development thereof in a bath containing an amount of thorium nitrate eifective to suppress the adsorptive capacity of said barite layer for thiosulfates.

'6. In the process 01 producing photographic prints by exposing, developing, fixing with sodium thiosuliate and washing photographic paper having a barite layer and a light-sensitive silver halide emulsion layer thereon, the improvement which comprises immersing said photographic paper after the development thereof in a bath containing an amount of cerous sulfate eflective to suppress the adsorptive capacity of said barite layer for thiosulfates. u

7. A photographic stop bath comprising water, acetic acid and a water-soluble rare earth metal salt.

8. A photographic silver halide fixing bath comprising a thiosuliate and a rare earth metal salt.

EDITH 'WEYDE. 

